Wrap spring starter



1952 s. GILBERT 2,583,829

WRAP SPRING STARTER Filed June 5, 1949 IN V EN TOR.

SAMUEL G/LBEPT Patented Jan. 29, 1 952 UNITED STATES PATENT OFFICE IWRAP SPRING STARTER.

Samuel Gilbert, Cedar Grove, N. J., assignor to Bendix AviationCorporation, Teterboro, N. J a corporation of Delaware Application June3, 1949, Serial No. 97,030

1 Claim. 1

This invention relates to engine starters, and more particularly to theengaging mechanism employed in starters for internal combustion engines.

In the conventional starter the engaging means usually comprises anengine jaw adapted to mesh with a clutch jaw mounted on a screw shaft.An axially stationary rotatable spline nut is threadably connected tothe screw shaft to cause it to move axially and mesh the clutch jaw withthe engine jaw. The spline nut is connected to the driving means by afriction disc pack. Usually an overrunning clutch is inserted in theengaging means in order to protect the starter mechanism when the enginespeed is above that of the starter. Although the above mechanism givesvery accurate control over the clutch setting and can carry the hightorques of larger engines, it can be seen that the conventional starteris quite complicated and expensive for use where accuracy and hightorque are not required.

It is an object of the present invention to avoid disadvantages ofapparatus of the aforesaid character and to do so by novel means.

Another object is to conserve weight and cost over a usual starterstructure.

Another object is to provide a simple engaging means which also limitstorque.

Another object is to provide a simple engaging means which performs thefunction of an overrunning clutch.

Another object is to provide engaging means to avoid the requirement ofaxial movement of the engaging member.

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one embodimentof the invention is illustrated by Way of example.

In the drawing the single figure is a vertical sectional view of anengine starter embodying the present invention.

Referring to the drawing, the device therein shown comprises a starterassembly including, in general, a motor l5, having a driving shaft l2rotatably supported by end wall M of motor housing [6, a pinion [8 shownas integral with the shaft l2 meshes with planet gears 20. The planetgears 20 are rotatably supported by stub shafts 22 carried by spidercage 24 which is rotatably mounted on shaft l2 by sleeve bearing 25. Theplanet gear 20 meshes with a ring gear 28 securely fastened againstrotation by screws 30 to gear housing 32. The gear housing 32 is securedto the motor housing l6 by screws 34 as shown or by other suitablemeans.

Integral with the spider cage 24 is a pinion 35 adapted to engage planetgear 38 which also engages the ring gear 28. The gears 38 are supportedby stub shafts 40 carried by a drum member 52. The drum member 42 isjournaled on the shaft [2 by the bearing 26 and by bearing surface 44 ofthe housing 32. A shoulder 46 on the drum 42 engages a shoulder 48 ofthe housing 32 to prevent axial movement of the drum 32.

The present invention provides a novel power transmission unit fordriving engagement with a crank shaft 50 or extension thereof of theengine to be started. It comprises a helical spring member 52 terminatedat one end by a shoulder 54 having splines 56 thereon for engagementwith corresponding splines in the drum 52 for rotation.

therewith. A retaining ring 58 holds the member 52 in engagement withthe drum 42. The other end is supported by a shell-like end portion 60secured with the housing 32 to crank case 62 by studs 54. The endportion 60 is adapted to hold a friction ring 66 for frictionallyholding one end of the spring member 52 to engage the latter to thecrank shaft 50. The internal diameter of the spring member in its freeposition is slightly greater than the outer diameter of the shaft 52.

In operation when the motor 20 is energized rotary motion is transmittedfrom the motor Ill through the shaft l2 to the planetary gear train thusrotating the drum 42 which through the splined connection rotates thehelical spring member 52. The ring 66 frictionally grips the free end ofthe helical spring member 52 causing it to wrap and close its diameterto frictionally grip the crank shaft. The friction ring is soproportioned as to have only sufificient friction force with the springmember 56 to cause it to grip the shaft and will permit the member 52 torotate after the frictional force is overcome. Thus rotary motion tocrank the engine is transmitted to the shaft 50. When the engine startsand rotates the shaft 50 at a greater speed than the drum 42 thefriction exerted by the shaft 50 against the spring member 52 tends tounwind it and releases it from the shaft 50.

The openings 68 in the friction ring retainer permit oil vapors from theengine to enter and lubricate crank shaft 5|] and helical spring member52. When thus lubricated, the spring member 52 limits the torque to adefinite predetermined maximum value. Thus when the engine offers undueresistance to cranking, the

3 spring 52 will slip on the shaft 50 thereby giving overloadprotection. Also if the engine backfires the torque limiting action ofthe device protects the starter and engine from reverse rotation.

It has been found in use that the bearings 44 and 26, and the end Wallmember [4 are sufiicient to prevent oil from entering the motor.However, it is understood that oil seals may be used if deemednecessary.

There is thus provided a novel starter in which a simple helical springmember replaces the usual spline nut, screw shaft, disc pack clutch andjaw clutch means.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangements of theparts, which will now appear to those skilled in the art, may be madewithout departing from the scope of the invention. Reference is,therefore, to be had to the appended claim for a definition of thelimits of the invention.

What is claimed is:

In a starter for an internal combustion engine, the combination adriving member, a helical spring clutch member operatively connected atone end to said driving member, the other end of said helical springmember terminating in a rigid ring-like section, a driven memberinterposed in said helical spring member, said helical spring memberincluding said ring-like section having a normal diameter slightlygreater than the diameter of said driven member, a friction ringsurrounding and in frictional engagement with said ring-like section,supporting means for said friction ring, said friction ring being soproportioned to frictionally grip said ring-like section upon rotationof said helical spring member in an engine cranking direction to causesaid helical spring member to grip the driven member while permittingthe helical spring member to be rotated by the driving member when thefrictional force of the ring is overcome by the force of rotation of thedriving member.

SAMUEL GILBERT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,940,880 Pitter Dec. 26, 19332,322,608 Webster June 22, 1943 2,347,788 Nardone May 2, 1944

